This invention relates generally to improvements in golf clubs, particularly with respect to improved club head attachment to the end of a golf club shaft and related improvements in club head weight distribution. More specifically, this invention relates to a slotted hosel for a golf club head wherein hosel weight at the heel end of the club head is reduced by formation of one or more slots in the hosel, in combination with improved apparatus and method for securely affixing the end of a club shaft to the slotted hosel.
Golf clubs are well known in the art and generally comprise an iron-style or so-called wood-style club head attached by means of an open-ended tubular hosel to the lower end of an elongated club shaft. The hosel comprises an upwardly open socket structure extending generally upwardly at an appropriate angle from the heel end of the club head for slide-fit reception of the lower end of the club shaft and related secure interconnection therewith as by means of a suitable epoxy adhesive or the like. In recent years, both iron-type and so-called metal wood-type club heads have been formed from metal such as stainless steel, titanium or titanium alloy, with considerable design effort directed to controlled and balanced distribution of club head weight to provide an optimized center of gravity or sweet spot for impact with a golf ball. However, the hosel presents a substantial off-center mass located at the heel end thereof where it complicates attempts to optimize balanced weighting of the club head.
In the past, modified hosel designs have envisioned the formation of external grooves in the hosel to reduce the hosel weight and thereby permit redistribution of the club head weight in a more advantageous manner. In particular, the weight removed from the grooved hosel can be redistributed in a controlled manner about the perimeter of the club head and/or ball impact face thereof, without increasing the overall club head weight, so that the club head center of gravity (i.e., the sweet spot) can be lowered and shifted toward a more centered position between the heel and toe of the club head. See, for example, U.S. Pat. Nos. 5,324,033 and 5,647,807. However, to avoid undesired weakening of the hosel/shaft attachment interface, such external hosel grooves have been relatively shallow and specifically have not been provided in the form of open slots extending radially through the hosel structure which would reduce the epoxy attachment area between the hosel and shaft. Unfortunately, this approach results in relatively minimal hosel weight reduction and a correspondingly minimal club head weight redistribution and related improvements in ball impact performance.
The present invention is specifically directed to the provision of a hosel structure of significantly reduced mass, by the formation of at least one and preferably multiple radially open slots formed in the hosel, to substantially reduce the hosel weight and thereby accommodate a significant redistribution of club head weight for improved, substantially optimized and consistent ball impact performance. The reduced mass hosel structure is provided without sacrificing the structural integrity or strength of the attachment interface with the end of the club shaft.
In accordance with the invention, a slotted hosel and related attachment system and method are provided for securely affixing a golf club head to the end of a golf club shaft. The hosel formed generally at a heel end of the club head incorporates at least one and preferably multiple laterally or radially open slots to significantly reduce the hosel weight or mass, and thereby permit redistibution of such weight or mass to the club head in a manner providing overall club head balance and weighting, and correspondingly improved ball impact performance.
The hosel is normally formed integral with a typically cast club head of the iron or so-called metal wood type to extend generally upwardly at an appropriate angle from the heel end of the golf club head. The hosel is suitably cast or machined to define an open-ended and generally cylindrical, upwardly open hosel bore. At least one and preferably multiple slots are formed through the hosel wall in a desired pattern to substantially reduce the weight of the hosel. A relatively thin-walled and preferably lightweight liner sleeve of titanium or the like is slide-fitted into the hosel bore and thereafter expanded as by application of hydraulic or other fluid pressure or mechanical means to create outwardly deformed dimples protruding partially into the hosel slots. These dimples in the liner sleeve provide a secure mechanical interlock between the hosel and liner sleeve. The end of the club shaft is thereafter slide-fitted into the liner sleeve and securely affixed thereto by means of a suitable epoxy adhesive or the like.
In a modified form of the invention, the mechanical interlock between the hosel and liner sleeve may be enhanced by additionally forming longitudinally elongated grooves within the hosel bore. In this embodiment, expansion of the liner sleeve to form the dimples is accompanied by additional liner sleeve expansion to form longitudinally elongated ridges interlocked with the hosel bore grooves. Further hosel/liner sleeve interlock can be obtained by means of a suitable epoxy adhesive or the like.
In a further variation of the invention, the axial length of the liner sleeve can be chosen so that an upper segment of the liner sleeve is extended and exposed above an upper margin of the hosel, when the liner sleeve is seated within the hosel bore. The exposed upper segment of the liner sleeve provides support for the club shaft at the hosel attachment site, and is particularly beneficial for closely controlling the flex characteristics of a nonmetal shaft, such as a club shaft formed from graphite materials or the like. In another variation, a small pilot port may be formed in the club head to extend generally coaxially from a lower or base end of the hosel bore to the lower margin of the club head. In this version, the pilot port accommodates partially filling of the lower end of a typically hollow tubular club shaft in the region of the hosel attachment interface with a resilient elastomer composition.
Other features and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of the example, the principles of the invention.